Compounds derived from diaminopyrazoles substituted by an aminoalkyl or aminoalkenyl radical and their use in oxidation dyeing of keratinous fibres

ABSTRACT

The invention concerns compounds derived from diaminopyrazole of formula (I), wherein: R 1  is a linear or branched radical selected among C 2 , C 3 , C 4  aminoalkyl radicals or C 2 , C 3 , C 4  aminoalkenyl radicals, or one of the physiologically acceptable salts thereof. The invention also concerns compositions containing said compound for dyeing keratinous fibers and the method using said compositions.

This application is a U.S. national phase application under 35 U.S.C. §371 of International Application No. PCT/FR02/02396 filed 9 Jul. 2002,which claims priority to French Application No. 01/09623 filed 18 Jul.2001, the entire disclosures of which are incorporated herein byreference.

The present invention relates to novel compounds derived fromdiaminopyrazole, to a composition for the oxidation dyeing of keratinfibers, and in particular of human keratin fibers such as the hair,comprising at least one compound derived from diaminopyrazole asoxidation base, and to the oxidation dyeing processes using it.

It is known practice to dye keratin fibers, and in particular humanhair, with dye compositions containing oxidation dye precursors, inparticular ortho- or para-phenylenediamines, ortho-aminophenols orpara-aminophenols and heterocyclic compounds such as diaminopyrazolederivatives, which are generally referred to as oxidation bases. Theoxidation dye precursors, or oxidation bases, are colorless or weaklycolored compounds which, when combined with oxidizing products, can giverise to colored compounds and dyes by a process of oxidativecondensation.

It is also known that the shades obtained with these oxidation bases canbe varied by combining them with couplers or coloration modifiers, thelatter being chosen in particular from aromatic meta-diamines,meta-aminophenols, meta-diphenols and certain heterocyclic compounds.

The variety of molecules used as oxidation bases and couplers makes itpossible to obtain a wide range of colors.

The so-called “permanent” coloration obtained by means of theseoxidation dyes must moreover satisfy a certain number of requirements.Thus, it must have no toxicological drawbacks and it must allow shadesof the desired strength to be obtained and have good resistance toexternal agents (light, bad weather, washing, permanent-waving,perspiration and friction).

The dyes must also allow white hairs to be covered, and, lastly, theymust be as unselective as possible, i.e. they must allow the smallestpossible differences in coloration to be produced over the entire lengthof the same keratin fiber, which may indeed be differently sensitized(i.e. damaged) between its tip and its root. They must also show goodchemical stability in the formulations, and must have a goodtoxicological profile.

Furthermore, for a certain number of applications, dyes that producechromatic shades on the hair are desired.

Application EP 375 977 discloses 4,5-diaminopyrazole compounds of use ascoloring agent in oxidation dyeing. Patent application EP 871 426 alsodiscloses compositions comprising 4,5-diaminopyrazole derivativessubstituted in the 1 position by an alkyl, mono- or polyhydroxyalkyl ormono- or polyaminoalkyl group, in combination with specific aminophenoland m-phenylenediamine couplers.

However, these dyes do not satisfy all the above requirements.

The Applicant has now discovered, entirely surprisingly andunexpectedly, that it is possible to obtain dyes, which are capable ofproducing powerful, particularly chromatic, bright and relativelyunselective colorations, which have excellent properties of resistanceto the various attacking factors to which keratin fibers may besubjected, by using as oxidation base the diaminopyrazoles of theformula (I) below or physiologically acceptable salts thereof.

One subject of the present invention is thus compounds derived fromdiaminopyrazole having the following structure (I):

in which R₁ is a linear or branched radical chosen from C₂, C₃ or C₄aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals.

The term “C₂, C₃ or C₄ alkyl radical” is understood to mean ahydrocarbonaceous radical with 2, 3 or 4 carbon atoms not comprisingunsaturation. In particular, it will relate to ethyl, n-propyl,isopropyl, n-butyl, isobutyl, tert-butyl or 2-methylpropyl radicals.

The term “C₂, C₃ or C₄ alkenyl radical” is understood to mean ahydrocarbonaceous radical with 2, 3 or 4 carbon atoms comprising one ortwo double bonds.

A subject of the invention is also the physiologically acceptable acidsalts of the compounds of formula (I), such as the hydrochlorides,hydrobromides, sulfates, tartrates, lactates or acetates.

A subject of the invention is also a composition for the oxidationdyeing of keratin fibers, and in particular of human keratin fibers suchas the hair, characterized in that it contains, in a medium that issuitable for dyeing, as oxidation base, at least one diaminopyrazole offormula (I) above, or physiologically acceptable acid salts thereof.

As mentioned above, the colorations obtained with the oxidation dyecomposition in accordance with the invention are powerful, particularlybright and chromatic. They in particular produce red shades that arefree of or contain very little blue or yellow. Furthermore, they showexcellent properties of resistance with respect to the action of variousexternal agents (light, bad weather, washing, permanent-waving,perspiration and friction).

A subject of the invention is also a process for the oxidation dyeing ofkeratin fibers using such a dye composition.

As examples of diaminopyrazoles of formula (I) according to theinvention, mention may be made of the following compounds:

Structure Name

2-(2-Amino-ethyl)-2H-pyrazole-3,4-diamine

2-(2,3-Diamino-propyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(2,3-Diamino-butyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-1-methyl)-propyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-propyl)-2H-pyrazole-3,4-diamine

2-(4-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(3,4-Diamino-butyl)-2H-pyrazole-3,4-diamine

4-(4,5-Diamino-pyrazol)-1-yl)-butane-1,2,3-triamine

2-(1-Aminomethyl-propyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-propyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(2,4-Diamino-butyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-1-methyl-propyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-1-aminomethl-propyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-1-aminomethyl-propyl)-2H-pyrazole-3,4-diamine

2-(3-amino-pro2-ene)-2H-pyrazole-3,4-diamine

2-(3-aminobut-3-ene)-2H-pyrazole-3,4-diamine

2-(2,3-diamino-1-aminomethyl-propyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-2-aminomethyl-propyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-prop-2-ene)-2H-pyrazole-3,4-diamine

2-(1-aminomethyl-prop-2-ene)-2H-pyrazole-3,4-diamine

2-(3-Amino-2-methyl-propyl)-2H-pyrazole-3,4-diamine

2-(4-amino-but-2-ene)-2H-pyrazole-3,4-diamine

The diaminopyrazoles of formula (I) that are preferred according to theinvention have the following structures:

Structure Name

2-(2-Amino-ethyl)-2H-pyrazole-3,4-diamine

2-(2,3-Diamino-propyl)-2H-pyrazole-3,4-diamine

2-(2-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(2,3-Diamino-butyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-propyl)-2H-pyrazole-3,4-diamine

2-(4-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(3,4-Diamino-butyl)-2H-pyrazole-3,4-diamine

4-(4,5-Diamino-pyrazol-1-yl)-butane-1,2,3-triamine

2-(2-Amino-propyl)-2H-pyrazole-3,4-diamine

2-(3-Amino-butyl)-2H-pyrazole-3,4-diamine

2-(2,4-Diamino-butyl)-2H-pyrazole-3,4-diamine

The diaminopyrazoles of formula (I) that are more particularly preferredaccording to the invention are 2-(2-aminoethyl)-2H-pyrazole-3,4-diamine,2-(3-aminopropyl)-2H-pyrazole-3,4-diamine,2-(2-aminopropyl)-2H-pyrazole-3,4-diamine,2-(4-aminobutyl)-2H-pyrazole-3,4-diamine and2-(3-aminobutyl)-2H-pyrazole-3,4-diamine, or the addition salts thereofwith physiologically acceptable acids.

The diaminopyrazoles of formula (I) according to the invention areprepared, for example, according to the following general preparationmethod:

The synthetic approach shown below is described in the literature up tointermediate (2) (J. H. P. Juffermanns, C. L.; Habraken; J. Org. Chem.,1986, 51, 4656; Klebe et al., Synthesis, 1973, 294; R. Hüttel, F.Büchele; Chem. Ber., 1955, 88, 1586).

The alkylation and the amination to obtain the compounds of the type (5)of formula (I) according to the invention are mentioned, for example, indocument DE 42 34 885.

The dye composition according to the invention especially contains from0.001% to 10% by weight, preferably from 0.05% to 6% by weight and evenmore preferably from 0.1% to 3% by weight of at least onediaminopyrazole of formula (I) or of the salts thereof.

The dye composition in accordance with the invention may also contain,in addition to the diaminopyrazole(s) defined above, at least oneadditional oxidation base that may be chosen from the oxidation basesconventionally used in oxidation dyeing and among which mention may bemade especially of para-phenylenediamines, bis(phenyl)alkylenediamines,para-aminophenols, ortho-aminophenols and heterocyclic bases other thanthe diaminopyrazoles used in accordance with the invention.

Among the para-phenylenediamines that may be mentioned moreparticularly, for example, are para-phenylenediamine,para-tolylenediamine, 2,6-dimethyl-para-phenylenediamine,2-β-hydroxyethyl-para-phenylenediamine,2-n-propyl-para-phenylenediamine, 2-isopropyl-para-phenylenediamine,N-(β-hydroxypropyl)-para-phenylenediamine,N,N-bis(β-hydroxyethyl)-para-phenylenediamine,4-amino-N-(β-methoxyethyl)aniline and the para-phenylenediaminesdescribed in French patent application FR 2 630 438, and the additionsalts thereof.

Among the bis(phenylalkylenediamines that may be mentioned moreparticularly, for example, areN,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)-1,3-diaminopropanol,N,N′-bis(β-hydroxyethyl)-N,N′-bis(4′-aminophenyl)ethylenediamine,N,N′-bis(4-aminophenyl)tetramethylenediamine,N,N′-bis(β-hydroxyethyl)-N,N′-bis(4-aminophenyl)tetramethylenediamine,N,N′-bis(4-methylaminophenyl)tetramethylenediamine andN,N′-bis(ethyl)-N,N′-bis(4′-amino-3′-methylphenyl)ethylenediamine, andthe addition salts thereof.

Among the para-aminophenols that may be mentioned more particularly, forexample, are para-aminophenol, 4-amino-3-methylphenol,4-amino-3-fluorophenol, 4-amino-3-hydroxymethylphenol,4-amino-2-methylphenol, 4-amino-2-hydroxymethylphenol,4-amino-2-methoxymethylphenol, 4-amino-2-aminomethylphenol and4-amino-2-(β-hydroxyethylaminomethyl)phenol, and the addition saltsthereof.

Among the ortho-aminophenols that may be mentioned more particularly,for example, are 2-aminophenol, 2-amino-5-methylphenol,2-amino-6-methylphenol and 5-acetamido-2-aminophenol, and the additionsalts thereof.

Among the heterocyclic bases that may be mentioned more particularly,for example, are pyridine derivatives, pyrimidine derivatives, pyrazolederivatives other than the diaminopyrazoles of formula (I) used inaccordance with the invention, and the addition salts thereof.

When they are used, these additional oxidation bases preferablyrepresent from 0.0005% to 12% by weight relative to the total weight ofthe dye composition and even more preferably from 0.005% to 6% by weightrelative this weight.

The oxidation dye compositions in accordance with the invention may alsocontain at least one coupler and/or at least one direct dye, especiallyto modify the shades or to enrich them with glints.

The couplers that may be used in the oxidation dye compositions inaccordance with the invention may be chosen from the couplersconventionally used in oxidation dyeing, and among which mention may bemade especially of meta-phenylenediamines, meta-aminophenols,meta-diphenols, mono- or polyhydroxylated naphthalene derivatives andheterocyclic couplers such as, for example, indole or pyridinederivatives, and the addition salts thereof.

These couplers are chosen more particularly from 2-methyl-5-aminophenol,5-N-(β-hydroxyethyl)amino-2-methylphenol,6-chloro-2-methyl-5-aminophenol, 3-aminophenol, 1,3-dihydroxybenzene,1,3-dihydroxy-2-methylbenzene, 4-chloro-1,3-dihydroxybenzene,2,4-diamino-1-(β-hydroxyethyloxy)benzene,2-amino-4-(β-hydroxyethylamino)-1-methoxybenzene, 1,3-diaminobenzene,1,3-bis(2,4-diaminophenoxy)propane, 3-ureidoaniline,3-ureido-1-dimethylaminobenzene, sesamol,1-β-hydroxyethylamino-3,4-methylenedioxybenzene, α-naphthol,2-methyl-1-naphthol, 6-hydroxyindole, 4-hydroxyindole,4-hydroxy-N-methylindole, 2-amino-3-hydroxypyridine,6-hydroxybenzomorpholine, 3,5-diamino-2,6-dimethoxypyridine,1-N-(β-hydroxyethyl)amino-3,4-methylenedioxybenzene and2,6-bis(β-hydroxyethylamino)toluene, and the addition salts thereof.

When they are present, these couplers especially represent from 0.0001%to 10% of the total weight of the dye composition, preferably from0.005% to 5% by weight and even more preferably from 0.1% to 3% of thisweight.

In general, the addition salts with an acid that may be used in thecontext of the dye compositions of the invention (oxidation bases andcouplers) are chosen especially from the hydrochlorides, hydrobromides,sulfates, tartrates, lactates and acetates.

The medium that is suitable for dyeing (or support) used according tothe invention consists of water or of a mixture of water and at leastone organic solvent chosen from C₁–C₄ lower alkanols, polyols and polyolethers, aromatic alcohols, similar products and mixtures thereof.

The dye composition according to the invention may also contain variousadjuvants conventionally used in compositions for dyeing the hair, suchas anionic, cationic, nonionic, amphoteric or zwitterionic surfactantsor mixtures thereof, anionic, cationic, nonionic, amphoteric orzwitterionic polymers or mixtures thereof, mineral or organicthickeners, antioxidants, reducing agents, sunscreens, penetratingagents, sequestering agents, fragrances, buffers, dispersants,conditioners, for instance silicones, film-forming agents, preservingagents and opacifiers.

The pH of the dye composition according to the invention is between 3and 12.

Needless to say, a person skilled in the art will take care to selectthis or these optional additional compound(s) such that the advantageousproperties intrinsically associated with the oxidation dye compositionin accordance with the invention are not, or are not substantially,adversely affected by the envisaged addition(s).

The dye composition according to the invention may be in various forms,such as in the form of liquids, creams or gels, or in any other formthat is suitable for dyeing keratin fibers, and especially human hair.

Another subject of the invention is a process for dyeing keratin fibers,and in particular human keratin fibers such as the hair, using the dyecomposition as defined above.

According to this process, at least one dye composition as defined aboveis applied to the fibers, for a time that is sufficient to develop thedesired coloration, either in air or using an oxidizing agent. The dyecomposition may optionally contain oxidation catalysts, so as toaccelerate the oxidation process.

According to a first embodiment of the process of the invention, thecoloration of the fibers may be performed without adding an oxidizingagent, solely by contact with atmospheric oxygen.

According to a second embodiment of the process of the invention, atleast one dye composition as defined above is applied to the fibers, thecolor being revealed at acidic, neutral or alkaline pH using anoxidizing agent that is added to the composition just at the time ofuse, or which is present in an oxidizing composition appliedsimultaneously or sequentially in a separate manner.

According to this second embodiment of the dyeing process of theinvention, the dye composition described above is preferably mixed, atthe time of use, with an oxidizing composition containing, in a mediumthat is suitable for dyeing, at least one oxidizing agent present in anamount that is sufficient to develop a coloration. The mixture obtainedis than applied to the keratin fibers and is left for an action time of3 to 50 minutes and preferably 5 to 30 minutes, after which the fibersare rinsed, washed with shampoo, rinsed again and dried.

The oxidizing agent present in the oxidizing composition as definedabove may be chosen from the oxidizing agents conventionally used forthe oxidation dyeing of keratin fibers, and among which mention may bemade of hydrogen peroxide, urea peroxide, alkali metal bromates andpersalts such as perborates and persulfates. Hydrogen peroxide isparticularly preferred.

The pH of the oxidizing composition containing the oxidizing agent asdefined above is such that, after mixing with the dye composition, thepH of the resulting composition applied to the keratin fibers preferablyranges between 3 and 12, and even more preferably between 5 and 11. Itis adjusted to the desired value by means of acidifying or basifyingagents usually used in the dyeing of keratin fibers, and as definedabove.

The oxidizing composition as defined above may also contain variousadjuvants conventionally used in compositions for dyeing the hair and asdefined above.

The composition that is finally applied to the keratin fibers may be invarious forms, such as in the form of liquids, creams or gels, or in anyother form that is suitable for dyeing keratin fibers, and especiallyhuman hair.

Another subject of the invention is a multi-compartment device or dyeing“kit” or any other multi-compartment packaging system, a firstcompartment of which contains the dye composition as defined above, anda second compartment of which contains the oxidizing composition asdefined above. These devices may be equipped with a means for applyingthe desired mixture to the hair, such as the devices described in patentFR-2 586 913 in the name of the Applicant.

The examples that follow are intended to illustrate the inventionwithout, however, limiting its scope.

EXAMPLES Synthetic Scheme with R₁=—NH—CO—O—C(CH₃)₃

Synthetic Example Synthesis of 2-(2-aminoethyl)-2H-pyrazole-3,4-diaminehydrobromide

Synthesis of 3,4,5-tribromopyrazole (1):

An aqueous solution (350 ml) containing sodium hydroxide (24 g, 0.6 mol)and pyrazole (10 g, 0.147 mol) was prepared with stirring (thetemperature of the reaction medium rose up to 35° C.). After cooling thereaction medium to 20° C., Br₂ (72 g, 0.45 mol) was added dropwise over1 hour, while maintaining the temperature between 20° C. and 25° C. Thereaction was monitored by thin layer chromatography (TLC). Theprecipitate was filtered off and washed with demineralized water (100ml). The filtrate was acidified to pH 6–7 using HCl (10%, 33 g, 0.27mol) and maintaining the temperature between 20 and 25° C. Theprecipitate thus formed was filtered off and washed with demineralizedwater (100 ml). The combined solids were maintained at reflux in aDean-Stark apparatus in the presence of toluene (200 ml). At the end ofcollection of the water, the organic phase was filtered while hot. Thesolvent was evaporated down to a residual volume of 110 ml. The solutionwas cooled to 0–50° C. for 1 hour. The precipitate formed was collectedby filtration, washed with cold toluene (20 ml) and dried under vacuumat 80° C. to give the 3,4,5-tribromopyrazole (1) in the form of anoff-white solid (30 g, 67%).

¹³C NMR (100 MHz, d₆-DMSO): 97.7, 116.1, 126.4 Melting point: 182–184°C.

Synthesis of 3,5-dibromo-4-nitropyrazole (2):

HNO₃ (d=1.50 g/ml; 18 ml, 0.429 mol) was added dropwise over 10 minutesto a solution of 3,4,5-tribromopyrazole (1) (50 g, 0.164 mol) in glacialacetic acid (750 ml) while maintaining the temperature at 15° C. Aceticanhydride (250 ml) was added and the reaction mixture was stirred atroom temperature for 2 hours. Once the reaction was complete, thereaction mixture was poured onto crushed ice (1 kg). After stirring for1 hour, the crude product was filtered off and then washed withdemineralized water (2×60 ml) to give crude1-nitro-3,4,5-tribromopyrazole. The water (24.6 ml) contained in the wetproduct was removed by heating a solution of the product in toluene (750ml) at reflux in a Dean-Stark apparatus. The toluene solution wasmaintained at reflux for a further 30 minutes until a TLC(eluent:toluene) showed that the rearrangement of the1-nitro-3,4,5-tribromopyrazole (Rf=0.77), the intermediate formed, into3,5-dibromo-4-nitropyrazole (2) (Rf=0.05) was complete. The solution wasconcentrated to a residual volume of 150 ml and then allowed to cool to60° C., followed by addition of hexane (275 ml). The solution was cooledto 0–5° C. for 1 hour and the 3,5-dibromo-4-nitropyrazole (2) (29.1 g,65%) was recovered by filtration and drying under vacuum in the form ofa pale yellow solid.

Melting point: 127.6–130.1° C.

Synthesis of [2-(3,5-dibromo-4-nitropyrazol-1-yl)ethyl]carbamic acidtert-butyl ester (3):

A solution of 3,5-dibromo-4-nitropyrazole (2) (16.0 g, 59 mmol) in DMF(130 ml) was added dropwise over 20 min to a stirred solution of NaH(2.6 g, 65 mmol; 60% dispersion in oil washed beforehand with hexaneunder an inert atmosphere) in DMF (80 ml). After stirring for 10 min, asolution of (2-bromoethyl)carbamic acid tert-butyl ester (19.85 g, 88.5mmol; obtained by reaction of 2-bromoethylamine withdi(tert-butyl)dicarabonate) in DMF (35 ml) was added dropwise over 10min. The reaction mixture was heated at 80° C. for 3 h and then the DMFwas evaporated under reduced pressure. A mixture of DCM/water (200 ml,1/1) was added to the residue and the organic phase was washed withwater (100 ml). The organic phase was dried over Na₂SO₄ and the solventwas evaporated under reduced pressure. The[2-(3,5-dibromo-4-nitropyrazol-1-yl)ethyl]carbamic acid tert-butyl ester(3.6 g, 15%) was obtained in the form of a pale yellow solid.

¹H NMR (400 MHz, d₆-DMSO): 7.02 (1H, t, CH₂CH₂NH), 4.29 (2H, t,CH₂CH₂NH), 3.37 (2H, m, CH₂CH₂NH), 1.35 (9H, s, CH₃).

Synthesis of[2-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)ethyl]carbamic acidtert-butyl ester (4):

A mixture of [2-(3,5-dibromo-4-nitropyrazol-1-yl)ethyl]carbamic acidtert-butyl ester (3.5 g; 8.45 mmol), EtOH (100 ml) and benzylamine (12.9g, 117 mmol) was heated at reflux for 1.5 h. The reaction medium wasconcentrated as much as possible under reduced pressure. The residue wastaken up in DCM (100 ml) and the organic phase was washed with water(5×50 ml) until all excess benzylamine had been removed and was thendried over Na₂SO₄. The organic solvent was evaporated under reducedpressure to give the[2-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)ethyl]carbamic acidtert-butyl ester (2.5 g, 67%) in the form of a pale yellow solid.

¹H NMR (400 MHz, d₆-DMSO): 8.00 (1H, t, NH_(Bn)) 7.32 (5H, m, H_(Bn)),7.05, (1H, t, NH_(BOC)), 4.70 (2H, d, J=8 Hz, CH_(2Bn)), 3.94 (2H, m,CH₂CH₂NH), 3.22 (2H, m, CH₂CH₂NH), 1.35 (9H, s, CH₃).Synthesis of 2-(2-aminoethyl)-2H-pyrazole-3,4-diamine hydrobromide (5):

A mixture of[2-(5-benzylamino-3-bromo-4-nitropyrazol-1-yl)ethyl]carbamic acidtert-butyl ester (2.1 g; 4.76 mmol) in EtOH (100 ml) containing a 5%Pd/C catalyst (Engelhard type, 50% moisture, 0.4 g wet weight) washydrogenated in an autoclave (250 ml) at 15 bar for 3 h. The catalystwas filtered off under an inert atmosphere and washed with EtOH, and thefiltrate was recovered in an ethanolic solution (25 ml) containinghydrobromic acid (47%, 2 ml). The orange-colored solution was evaporatedto dryness to give the 2-(2-aminoethyl)-2H-pyrazole-3,4-diamine in thehydrobromide form (3.55 HBr) as a pale pink solid (1.5 g, 92%).

Elemental analysis (C₅H₁₁N₄, 3.55 HBr; MW=428.41 g/mol) Found: C:14.82%, H: 3.35%, N: 16.99%, Br: 62.89%. Theory: C: 14.02%. H: 3.42%, N:16.35%, Br: 66.21%.

¹H NMR (400 MHz, d₆-DMSO): 9.62 (2H, S_(broad), HBr), 7.98 (2H,S_(broad), CH₂CH₂NH₂), 7.37 (1H, s, H_(pyrazole)), 6.68 (4H, S_(broad),NH₂), 4.17 (2H, t, CH₂CH₂NH₂), 3.21 (2H, m, CH₂CH₂NH₂).

Examples of Dye Composition in Alkaline Medium

The following composition is prepared:

diaminopyrazole base of formula (I) 5 × 10⁻³ mol coupler 5 × 10⁻³ mololeyl alcohol polyglycerolated with 4.0 g 2 mol of glycerol oleylalcohol polyglycerolated with 5.7 g A.M. 4 mol of glycerol, containing78% active material (A.M.) oleic acid 3.0 g oleylamine containing 2 molof ethylene 7.0 g oxide, sold under the trade name Ethomeen O12 by thecompany Akzo diethylaminopropyl laurylamino succinamate, 3.0 g A.M.sodium salt, at 55% A.M. oleyl alcohol 5.0 g oleic acid diethanolamide12.0 g propylene glycol 3.5 g ethyl alcohol 7.0 g dipropylene glycol 0.5g propylene glycol monomethyl ether 9.0 g sodium metabisulfite as anaqueous 0.455 g A.M. solution containing 35% A.M. ammonium acetate 0.8 gantioxidant, sequestering agent qs fragrance, preserving agent qsaqueous ammonia containing 20% NH₃ 100 g pH = 9.5 A.M. means “activematerial”

The base and the coupler are as defined below.

DYEINGS AT ALKALINE pH Examples Base Coupler 1 2-(2-aminoethyl)-2H-m-aminophenol pyrazole-3,4-diamine 2 2-(2-aminoethyl)-2H-6-chloro-2-methyl-5- pyrazole-3,4-diamine aminophenol 32-(2-aminoethyl)-2H- 2,4-diamino-1(β- pyrazole-3,4-diaminehydroxyethyloxy)- benzene dihydrochloride 4 2-(2-aminoethyl)-2H-2-methyl-5-aminophenol pyrazole-3,4-diamine

At the time of use, each dye composition is mixed, weight for weight,with a 20-volumes aqueous hydrogen peroxide solution (6% by weight), thepH of which has been adjusted to about 2.5 with orthophosphoric acid.

The mixture is applied to natural gray hair containing 90% white hairs,at a rate of 5 g per 0.5 g of hair.

After 30 minutes, the hair is then rinsed, washed with a standardshampoo, rinsed again and dried.

The color of the locks was evaluated in the L*a*b* system, on whitehair, using a Minolta CM 2002 spectrophotometer.

In the L*a*b* space, the lightness is indicated by the value L* on ascale from 0 to 100, while the chromatic data is expressed by a* and b*which indicate two color axes, a* the red-green axis and b* theyellow-blue axis.

According to this system, the higher the value of L, the paler and lessintense the color. Conversely, the lower the value of L, the darker ormore intense the color.

White hair Examples L* a* b* Example 1 35.1 27.5 13.9 Example 2 41.925.0 15.2 Example 3 30.7 21.3 2.1 Example 4 41.8 27.1 24.5

The diaminopyrazoles according to the invention thus make it possible toobtain strong and chromatic shades at alkaline pH.

Example of Dye Composition in Neutral Medium

The same formulations as above are prepared, replacing the aqueousammonia with citric acid in an amount such that the pH is equal to 7.

DYEING AT NEUTRAL pH Example Base Coupler 5 2-(2-aminoethyl)-2H-2-methyl-5- pyrazole-3,4-diamine aminophenol

Locks of natural and permanent-waved gray hair containing 90% whitehairs are dyed with the dye composition 5 and 6 above in the same manneras for the dyeing at alkaline pH.

The following shades are obtained:

Natural white hair Example L* a* b* Example 5 41.6 17.8 17.8

At neutral pH, the diaminopyrazoles according to the invention make itpossible to obtain strong shades.

1. A diaminopyrazole compound of formula (I):

in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, and wherein thecompound of formula (I) is further defined as2-(2-aminoethyl)-2-H-pyrazole-3,4-diamine,2-(3-aminopropyl)-2H-pyrazole-3,4-diamine,2-(2-aminopropyl)-2H-pyrazole-3,4-diamine,2-(2,3-diamino-propyl)-2H-pyrazole-3,4-diamine,2-(4-aminobutyl)-2H-pyrazole-3,4-diamine,2-(3-aminobutyl)-2H-pyrazole-3,4-diamine,2-(2-aminobutyl)-2H-pyrazole-3,4-diamine,2-(3,4-diaminobutyl)-2H-pyrazole-3,4-diamine,2-(2,4-diaminobutyl)-2H-pyrazole-3,4-diamine,2-(2,3-diaminobutyl)-2H-pyrazole-3,4-diamine,4-(4,5-diaminopyrazol-1-yl)-butane-1,2,3-triamine,2-(3-amino-1-methylpropyl)-2H-pyrazole-3,4-diamine,2-(2-amino-1-methyl-propyl)-2H-pyrazole-3,4-diamine,2-(1-aminomethylpropyl)-2H-pyrazole-3,4-diamine,2-(3-amino-1-amino-methylpropyl)-2H-pyrazole-3,4-diamine,2-(2-amino-1-aminomethylpropyl)-2H-pyrazole-3,4-diamine,2-(2,3-diamino-1-aminomethylpropyl)-2H-pyrazole-3,4-diamine,2-(3-amino-2-methylpropyl)-2H-pyrazole-3,4-diamine,2-(3-amino-2-aminomethylpropyl)-2H-pyrazole-3,4-diamine,2-(3-aminoprop-2-ene)-2H-pyrazole-3,4-diamine,2-(2-aminoprop-2-ene)-2H-pyrazole-3,4-diamine,2-(4-aminobut-2-ene)-2H-pyrazole-3,4-diamine,2-(3-aminobut-3-ene)-2H-pyrazole-3,4-diamine,2-(1-aminomethylprop-2-ene)-2H-pyrazole-3,4-diamine, or aphysiologically acceptable acid salt of any of these.
 2. The compound ofclaim 1, wherein the physiologically acceptable salt is a hydrochloride,hydrobromide, sulfate, tartrate, lactate, or acetate.
 3. A compositionfor the oxidation dyeing of keratin fibers, comprising, as an oxidationbase, a diaminopyrazole compound of formula (I):

in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, or aphysiologically acceptable salt thereof, in a medium suitable for dying.4. The composition of claim 3, further defined as comprising from 0.001%to 10% by weight of at least one diaminopyrazole of formula (I) or saltthereof.
 5. The composition of claim 3, wherein the medium that issuitable for dyeing comprises water or a mixture of water and at leastone organic solvent further defined as a C₁–C₄ lower alkanol, polyol,polyol ether, or aromatic alcohol, or a mixture thereof.
 6. Thecomposition of claim 3, further defined as having a pH of between 3 and12.
 7. The composition of claim 3, comprising at least one additionaloxidation base further defined as a para-phenylenediamine,bis(phenyl)alkylenediamine, para-aminophenol, ortho-aminophenol, orheterocyclic base other than the diaminopyrazole of formula (I), or anaddition salt of one of these with an acid.
 8. The composition of claim7, wherein the additional oxidation base comprises from 0.0005% to 12%by weight relative to the total weight of the dye composition.
 9. Thecomposition of claim 3, further defined as comprising at least onedirect dye.
 10. The composition of claim 3, further defined ascomprising at least one coupler.
 11. The composition of claim 10,wherein the coupler is a meta-phenylenediamine, meta-aminophenol,meta-diphenol, monohydroxylated naphthalene derivative, polyhydroxylatednaphthalene derivative, or heterocyclic coupler, or an addition salt ofone of these with an acid.
 12. The composition of claim 10, wherein thecoupler represents from 0.0001% to 10% by weight relative to the totalweight of the dye composition.
 13. The composition of claim 3, furtherdefined as comprising at least one direct dye and at least one coupler.14. A process for dyeing keratin fibers, comprising applying to thefibers a composition comprising, as an oxidation base, a diaminopyrazolecompound of formula (I):

in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, or aphysiologically acceptable salt thereof, in a medium suitable for dying,for a time that is sufficient to develop the desired coloration, eitherin air or using an oxidizing agent.
 15. The process of claim 14, whereinthe keratin fibers are further defined as human hair.
 16. The process ofclaim 14, further comprising applying to the fibers an oxidationcatalyst.
 17. The process of claim 14, wherein no oxidizing agent isapplied and coloration is revealed by contact with atmospheric oxygen.18. The process of claim 14, further comprising an application of anoxidizing agent to the fibers.
 19. The process of claim 18, wherein theoxidizing agent is added to the dye composition prior to application ofthe dye composition to the fibers.
 20. The process of claim 18, whereinthe oxidizing agent is comprised in an oxidizing composition that isapplied simultaneously or sequentially with regard to the dyeingcomposition to the fibers.
 21. The process of claim 18, wherein theoxidizing agent is hydrogen peroxide, urea peroxide, an alkali metalbromate, or a persalt.
 22. A kit comprising: a first compartmentcontaining a composition comprising a diaminopyrazole compound offormula (I):

 in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, or aphysiologically acceptable salt thereof, in a medium suitable for dying;and a second compartment containing an oxidizing composition.
 23. Acomposition for oxidation dyeing of keratin fibers comprising, as anoxidation base, from 0.001% to 10% by weight of at least onediaminopyrazole of formula (I):

in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, or aphysiologically acceptable salt thereof, in a medium suitable for dying.24. A process for dyeing human hair, comprising applying to the hair acomposition comprising, as an oxidation base, a diaminopyrazole compoundof formula (I):

in which R₁ is a linear or branched radical further defined as a C₂, C₃or C₄ aminoalkyl or C₂, C₃ or C₄ aminoalkenyl radicals, or aphysiologically acceptable salt thereof, in a medium suitable for dying,for a time that is sufficient to develop the desired coloration, eitherin air or using an oxidizing agent.